Particulate sampling system and method

ABSTRACT

A method for controlling the flow through an exhaust sampling system includes sensing an operating characteristic of a power source, extracting a sample of an exhaust flow of the power source, combining the sample with an additional flow of fluid, and measuring a particulate level of the combined flow. A flow rate of the extracted sample is controlled to be substantially proportional to a flow rate of the exhaust flow based on a difference between the combined flow and the additional flow.

TECHNICAL FIELD

The present disclosure relates to a system and method for measuring theamount of particulate matter present in a flow of fluid and, moreparticularly, to a system and method for controlling fluid flow througha proportional exhaust sampling system connected to a power source.

BACKGROUND

Exhaust emissions from motorized on-highway machines are regulated bythe federal government and must not exceed certain contaminant levels asset forth in Title 40, Chapter 1 of the Code of Federal Regulations,Section 86 Subpart C. For example, some government regulations placelimits on the amount of particulate matter that may be emitted by dieseltruck engines. These regulations specify the acceptable level ofparticulate matter that may be carried in the exhaust gas stream of theengine. Particulate matter may include, for example, carbonparticulates, unburned hydrocarbons, and sulphates.

Due to these regulations, equipment has been developed to test andanalyze machine engines and/or other power sources for conformance withgovernment standards. In particular, partial flow exhaust gas samplingsystems have been developed in an effort to certify such power sourcesas being in compliance with government emissions regulations. Generally,these systems operate by extracting a small portion of a power sourceexhaust flow. A regulated flow of filtered ambient air is then mixedwith the extracted portion, and the combined flow is directed to afilter configured to trap the particulate matter contained within thecombined flow. The power source may then be evaluated based on thequantity of particulate matter trapped by the filter during a particulartest cycle.

One such system is described in U.S. Pat. No. 6,062,092 to Weaver (“the'092 patent). The system of the '092 patent utilizes a feedbackarrangement to change the proportion of exhaust gas being extracted fromthe power source exhaust flow relative to the total flow of exhaust.Although the system changes this proportion based on changes in theexhaust flow of the power source, the system uses the pressuredifferential between the exhaust gas flow stream and the pressure insidea sampling probe for feedback. As a result, the system of the '092patent does not take into account variations in the combined flow seenby the filter when determining the amount of exhaust flow to extract.Such variations may be caused by, for example, exhaust flow excursionsand/or other system based factors.

The systems and methods of the present disclosure are directed toovercome one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one embodiment of the present disclosure, a method for controllingthe flow through an exhaust sampling system includes sensing anoperating characteristic of a power source, extracting a sample of anexhaust flow of the power source, combining the sample with anadditional flow of fluid, and measuring a particulate level of thecombined flow. A flow rate of the extracted sample is controlled to besubstantially proportional to a flow rate of the exhaust flow based on adifference between the combined flow and the additional flow.

In another embodiment of the present disclosure, a method of controllingfluid flow through an exhaust sampling system connected to a powersource includes controllably extracting a portion of an exhaust flow ofthe power source, directing the portion through a dilution device, andcombining the portion with a treated flow of fluid. A mass flow rate ofthe extracted portion is controlled to be substantially proportional toa mass flow rate of the exhaust flow of the power source based on adifference between a mass flow rate of the combined flow and a mass flowrate of the treated flow.

In still another embodiment of the present disclosure, an exhaustsampling system includes a first flow sensor fluidly connected to acompressed air source and configured to sense a characteristic of adilute flow, a flow control valve fluidly connected to the first flowsensor and configured to controllably direct the dilute flow to adilution device, and a second flow sensor fluidly connected downstreamof the dilution device and configured to sense a characteristic of acombined flow. The exhaust sampling system further includes a controllerconfigured to control a mass flow rate of a flow of exhaust gasextracted by a component of the dilution device based on a differencebetween the sensed characteristic of the dilute flow and the sensedcharacteristic of the combined flow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of a test cell according to anexemplary embodiment of the present disclosure;

FIG. 2 is a diagrammatic illustration of a sampling system according toan exemplary embodiment of the present disclosure; and

FIG. 3 is a flow chart of a sampling strategy according to an exemplaryembodiment of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a test cell 100 according to an exemplary embodimentof the present disclosure. The test cell 100 includes a power source 10mechanically and electrically coupled, and/or otherwise connected to adynamometer 14. An air filter 4, a temperature and humidity controldevice 6, and a flow management device 8 may also be fluidly connectedto, for example, an intake manifold of the power source 10. In addition,an exhaust manifold or other exhaust release device of the power source10 may be fluidly connected to an evacuation system 18 of the test cell100. The evacuation system 18 may include, for example, an exhaust fanand/or one or more filters configured to extract, for example,particulates and/or other harmful pollutants. The evacuation system 18may also include, for example, a vacuum source or other deviceconfigured to act on exhaust gases from the power source 10 and/or theexhaust sampling system 20. The evacuation system 18 may be configuredto release the exhaust gases to the environment.

As shown in FIG. 1, an exhaust sampling system 20 may be fluidly and/orotherwise connected to the power source 10, and an extraction component56 of the exhaust sampling system 20 may be configured to extract aportion of an exhaust flow of the power source 10. The exhaust samplingsystem 20 may include an exhaust sampling system controller 22 disposedwithin the test cell 100 and electrically connected to components of theexhaust sampling system 20 and/or the test cell 100. For example, theexhaust sampling system controller 22 may be configured to communicateelectrically with the flow management device 8 and/or a test cellcontroller 24. As shown in FIG. 1 the power source 10 may also befluidly connected to a fuel system 16 configured to supply fuel to thepower source 10. Although not shown in FIG. 1, it is understood that thefuel system 16 may include, for example, a fuel pump, a fuel tank, aflow meter, a plurality of valves, and/or other conventional componentsconfigured to supply a regulated flow of fuel to the power source 10.These components may also be configured to measure, for example, thequantity, flow rate, and/or other characteristics of the flow of fuelsupplied to the power source 10.

One or more of the components discussed above may be connected to eachother via a flow line 26. For example, the air filter 4 may be connectedto the temperature and humidity control device 6 via a flow line 26, andthe temperature in humidity control device 6 may be connected to theflow management device 8 via a flow line 26. The fuel system 16 may beconnected to the power source 10 via a fuel line 30 and the power source10 may be connected to the evacuation system 18 via an exhaust line 58.In an exemplary embodiment, the fuel line 30 and the exhaust line 58 maybe flow lines 26. The extraction component 56 of the exhaust samplingsystem 20 may be connected to the exhaust line 58, and the extractioncomponent 56 may be configured to extract a portion of an exhaust flowof the power source 10 passing through the exhaust line 58. The exhaustsampling system 20 may also be connected to the evacuation system 18 viaa flow line 26, and the exhaust sampling system 20 may be configured todirect a flow of fluid to the evacuation system 18 during and/or after asampling cycle. The power source 10 may also be connected to thedynamometer 14 via a mechanical and/or other conventional link 28.

As illustrated in FIG. 1 the temperature and humidity control device 6,the flow management device 8, the power source 10, the dynamometer 14,the fuel system 16, and/or the exhaust sampling system controller 22 maybe electrically connected to the test cell controller 24 via controllines 32. In addition the flow management device 8 may be electricallyconnected to the exhaust sampling system controller 22 via a controlline 32. The control lines 32 may enable each of the above components tocommunicate and/or otherwise send sensed information, control signals,and/or other electrical signals to the test cell controller 24 and/orthe exhaust sample system controller 22. The control lines 32 may alsoenable the test flow controller 24 and/or the exhaust sampling systemcontroller 22 to send control signals to each of the connectedcomponents.

The power source 10 illustrated in FIG. 1 may be, for example, any sparkignition engine, diesel engine, and/or other source of mechanical orelectrical power known in the art. The dynamometer 14 may be anyconventional device used to measure, for example, rpm, torque, and/orother power source operating characteristics from which the output powerproduced by the power source can be calculated. The air filter 4 may beany conventional filter device configured to, for example, captureand/or otherwise trap dirt and other airborne particles before suchparticles pass to the power source 10 Such particles may cause damageto, for example, power source cylinders, walls, pistons and pistonrings. The air filter 4 may include, for example, a replaceable filterelement configured to assist in the capture and/or removal of airborneparticles.

The exhaust sampling system controller 22 and/or the test cellcontroller 24 may be, for example, a central processing unit, anelectronic control module, a computer, a radio transmitter, or any othertype of controller known in the art. The controllers 22, 24 may beconnected to an operator interface (not shown) such as, for example, akeyboard, monitor, printer, touch screen, control panel, or any otherdevice enabling a user to enter commands and/or receive sensed and/orcalculated information from components of the test cell 100 and/or theexhaust sampling system 20. In an exemplary embodiment, the controllers22, 24 may control aspects of the power source test/certification cycleand may be configured to store information for later retrieval and use.

The temperature and humidity control device 6 may be configured to senseand/or control the temperature and/or humidity of the filtered ambientair before it enters the power source 10. The temperature and humiditycontrol device may include, for example, a thermocouple, a hygrometer, aheat exchanger, and/or other conventional components configured toassist in sensing and/or controlling temperature and humidity. The flowmanagement device 8 may be any device or combination of devicesconfigured to measure and/or regulate, for example, the flow rate,pressure, and/or other flow characteristics of a fluid flow. In anexemplary embodiment, the flow management device 8 may include a laminarflow element and/or a pressure differential transducer configured tosense changes in the pressure and/or flow rate of a fluid passingthrough the flow management device 8 and/or other components of the testcell 100. Each of the test cell components discussed above is known inthe art and these components will not be discussed in further detail inthe present disclosure. Further, it is understood that each of the dashlines in FIG. 1 illustrate a control line 32 and that each of the solidlines in FIG. 1 represents a flow line 26 with the exception of theextraction component 56, the exhaust line 58, and the link 28.

Referring now to FIG. 2, an exhaust sampling system 20 in accordancewith an exemplary embodiment of the present disclosure includes a diluteside 106 and a total side 108. A dilution device 54 of the dilute side106 may be fluidly connected to the exhaust line 58 of the power source10 (FIG. 1), and the dilute side 106 may further include, for example, acompressed air source 38, a flow treatment device 40, a chiller 42, aflow sensor 46, and a plurality of flow control and/or other types ofvalves. In addition, the dilution device 54 of the dilute side 106 maybe fluidly connected to a filter 62 of the total side 108, and the totalside 108 may further include, for example, a flow sensor 76, a vacuum80, and a plurality of flow control and/or other types of valves. Theexhaust sampling system controller 22 and/or the test cell controller 24(FIG. 1) may be electrically connected to one or more of the componentsof the exhaust sampling system 20. It is understood that each of thedash lines illustrated in FIG. 2 are control lines 32 and each of thesolid lines connecting the components of the exhaust sampling system 20illustrated in FIG. 2 are flow lines 26.

As will be described in greater detail below, the components of thedilute side 106 may be configured to compress, treat, cool, measure,and/or regulate a dilute flow 36 of ambient air. The dilute flow 36 maybe combined with a flow of exhaust gas that is extracted from theexhaust flow of the power source 10. In addition, the flow rate of thedilute flow 36 may be rapidly adjusted by the dilute side components inresponse to the sensed difference between the flow rate of the diluteflow 36 and the flow rate of the combined (dilute and extracted) flow.

The compressed air source 38 may include, for example, an air compressoror any other device capable of compressing a gas and delivering thecompressed gas through the flow lines 26. For example, in one embodimentof the present disclosure the compressed air source 38 may be a shop aircompressor of a type known in the art and may supply compressed air atapproximately 70 to 110 psi. This range may be increased or decreaseddepending on the size of the compressed air source 38 used. Thecompressed air source 38 may be configured to deliver a substantiallyconstant, substantially uniform flow of compressed air to the componentsof the exhaust sampling system 20. As illustrated in FIG. 2. A diluteflow 36 may enter an intake of the compressed air source 38 and may becompressed therein.

The compressed air source 38 may be fluidly connected to a flowtreatment assembly 40 via a flow line 26. The flow lines 26 of thepresent disclosure may be any type of tubing, piping, or hose known inthe art. The flow lines 26 may be, for example, plastic, rubber,aluminum, copper, steel, or any other material capable of delivering acompressed gas in a controlled manner, and may be flexible or rigid. Thelength of the flow lines 26 may be minimized to facilitate operation ofthe exhaust sampling system 22, while reducing the pressure drop betweenthe components thereof.

The flow treatment assembly 40 may be any assembly and/or collection ofcomponents configured to filter, treat, and/or otherwise clean thedilute flow 36. In an exemplary embodiment, the flow treatment assembly40 may include a charcoal scrubber, a dessecator and/or a particulatefilter (not shown). It is understood that the components of the flowtreatment assembly 40 may be separate devices disposed within a singlehousing. Alternatively, the components of the flow treatment assembly 40may be disposed in separate housings. The charcoal scrubber of the flowtreatment assembly 40 may be configured to remove, for example,hydrocarbons from the dilute flow 36. The dessecator of the flowtreatment assembly 40 may be configured to remove, for example, waterfrom the dilute flow 36, and the particulate filter may be an ultra fineparticulate filter of a type known in the art. Such particulate filtersmay be configured to capture and/or remove impurities contained withinthe dilute flow 36, such as, for example, sluff from the dessecator,charcoal from the charcoal scrubber, and/or any other airborneimpurities. The flow treatment assembly 40 may be connected to a chiller42 via a flow line 26.

The chiller 42 may be any device or combination of devices configured toreduce the temperature of a flow fluid passing therethrough. The chiller42 may be connected to, for example, a source of coolant to assist inreducing the temperature of the fluid flow passing therethrough. Thechiller 42 may include, for example, a heat exchanger such as, forexample, a radiator and/or any other conventional heat exchange device.In an exemplary embodiment of the present disclosure, the chiller 42 maybe configured to reduce the temperature of the dilute flow 36 toapproximately 20° C. The chiller 42 may be fluidly connected to a flowsensor 46 via a flow line 26, and an isolation valve 44 may be disposedwithin the flow line 26 between the chiller 42 and the flow sensor 46.It is understood that in an exemplary embodiment, the compressed airsource 38, the flow treatment assembly 40, and/or the chiller 42 may beindependently controllable and, thus, may not be electrically connectedto the exhaust sampling system controller 22.

The isolation valve 44 may be any type of controllable fluid valve knownin the art such as, for example, a poppet valve, a butterfly valve, or aball valve. The isolation valve 44 may be controlled to completelyrestrict a flow of air from passing therethrough or may allow the flowto pass unrestricted. In an exemplary embodiment, the isolation valve 44may be a ball valve configured to substantially fully open and/orsubstantially fully close fluid communication between, for example, thechiller 42 and the flow sensor 46. The isolation valve 44 may becontrolled by any conventional pneumatic and/or electric actuator suchas, for example, a solenoid.

The flow sensor 46 may be any device and/or collection of devicesconfigured to sense the volumetric flow rate and/or othercharacteristics of a flow passing therethrough. In an exemplaryembodiment, the flow sensor 46 may include a laminar flow elementconfigured to measure the volumetric flow rate of the dilute flow 36.The laminar flow element may include, for example, a matrix of smalltubes in, for example, a honeycomb arrangement, and the laminar flowelement may be any conventional type of laminar flow element known inthe art.

In addition to the laminar flow element discussed above, the flow sensor46 may further include one or more components configured to sense, forexample, the pressure and/or temperature of the dilute flow 36 passingthrough the flow sensor 46. Such pressure and/or temperaturemeasurements may be used to derive the density of the dilute flow 36.Thus, the exhaust sampling system controller 22 may use the volumetricoutput of the laminar flow element in conjunction with the densityoutput of these additional components to determine, for example, themass flow rate of the dilute flow 36.

The additional components of the flow sensor 46 may include, forexample, a pressure differential transducer, an absolute pressuretransducer, and a platinum resistance thermistor. Although theseadditional elements are not shown in FIG. 2 it is understood that thepressure differential transducer may include one or more pressuresensors disposed upstream and/or downstream of the laminar flow elementand configured to measure a pressure drop across the laminar flowelement. The absolute pressure transducer may be disposed upstream ofthe laminar flow element and may be configured to measure the absolutepressure of, for example, the dilute flow 36. In addition the platinumresistance thermistor may be disposed immediately upstream of an inletof the laminar flow element and may be configured to sense thetemperature of the dilute flow 36 entering the laminar flow element. Theplatinum resistance thermistor may be inherently stable due to theplatinum and/or other metals utilized within the thermistor, and may beconfigured to make relatively fine and/or accurate temperaturemeasurements.

The flow sensor 46 may be fluidly connected to the dilution device via aflow line 26, and a flow control valve 50 may be disposed in the flowline 26. The flow control valve 50 may be any type of controllable fluidvalve known in the art configured to regulate a pressurized flow offluid. The flow control valve 50 may be configured to rapidly respond tocontrol signals sent from, for example, the exhaust sampling systemcontroller 22.

The flow control valve 50 may be, for example, an electromagnetic valvehaving a plunger maintained in a magnetic field such that the mechanicalresistance placed on the plunger is substantially zero while the flowcontrol valve 50 is in use. The flow control valve 50 may be, thus,substantially instantly variable. The flow control valve 50 may have aresponse time of less than or equal to 75 milliseconds and may beconfigured to receive and react to substantially continuous flowcommands sent by the exhaust sampling system controller 22. The flowcontrol valve 50 may be configured to adjust the flow rate of the diluteflow 36 and/or the extracted flow according to the flow commands. Theflow commands may be in response to, for example, the volumetric and/ormass difference between a combined flow 37 and the dilute flow 36.

The flow control valve 50 may also be configured to control theproportionality of the exhaust flow sample that is extracted from theexhaust flow of the power source 10 (FIG. 1). As used herein, the term“proportionality” is defined as the amount of exhaust flow that isextracted relative to the total exhaust flow 34 produced by the powersource 10 at the time of the extraction.

In an exemplary embodiment of the present disclosure the exhaustsampling system 20 may further include a venturi 48. The venturi 48 maybe, for example, a critical flow of venturi and/or any other type ofventuri known in the art. As illustrated in FIG. 2, an inlet of theventuri 48 may be fluidly connected downstream of an outlet of the flowsensor 46 and upstream of an inlet of the flow control valve 50. Anoutlet of the venturi 48 may also be connected to the flow line 26downstream of an outlet of the flow control valve 50 and upstream of avalve 52. In an exemplary embodiment the venturi 48 may be sized and/orotherwise configured to receive approximately 80% of the maximum flowpassing through a dilute side 106 of the exhaust sampling system 20. Insuch an embodiment the remaining 20% of the maximum flow travelingthrough the dilute side 106 may be controlled by the flow control valve50. The venturi 48 may be configured to sense, for example, the flowrate and/or other characteristics of the dilute flow 36 passing throughthe dilute side 106 of the exhaust sampling system 20. The venturi 48may be electrically connected to, for example, the exhaust samplingsystem controller 22 and may be configured to transmit, for example,sensed flow information thereto. It is understood that, in otherexemplary embodiments of the present disclosure, the venturi 48 may beomitted. In such embodiments, the flow control valve 50 may be a singlepoint of flow control.

An outlet of the flow control valve 50 may be fluidly connected to aninlet of the valve 52 via a flow line 26. The valve 52 may be a standardtwo-way valve, three-way valve, or any other type of controllable flowvalve known in the art. In an exemplary embodiment, the valve 52 may beconfigured to direct the dilute flow 36 to pass from the dilute side 106to a total side 108 of the exhaust sampling system 20 via a bypass line66. In addition, the valve 52 may be configured to transmit the diluteflow 36 to an inlet of a dilution device 54 while substantiallycompletely restricting flow from the dilute side 106 through the bypassline 66.

As discussed above, an extraction component 56 of the dilution device 54may be disposed within and/or fluidly connected to an exhaust line 58.The extraction component 56 may be configured to extract at least aportion of the exhaust flow 34 of the power source 10 during operation.The extraction component 56 may be fluidly connected to the dilutiondevice 54 such that the extracted portion of the exhaust flow 34 may bedelivered to the dilution device 54 through the extraction component 56.

The dilution device 54 may be a flow tunnel and/or other type ofdilution device known in the art. For example, the dilution device 54may include an air distribution tube and a central axis (not shown). Theair distribution tube may be an elongate cylindrical tube of, forexample, stainless steel or other like materials. The cylindrical tubemay include a plurality of distribution holes formed in a central regionof the cylindrical tube. The dilution device 54 may also include ahousing forming an annular chamber peripherally about the central regionof the cylindrical tube. The dilution device 54 may further include acenter tube means for defining a second annular chamber within thecylindrical tube along the central axis. In an exemplary embodiment, thecenter tube means may be formed of centered stainless steel, or otherlike materials, and the porous center tube may include a plurality ofrelatively small pores opening inwardly into an internal passage.

The dilution device 54 may be configured to receive the dilute flow 36and may combine the dilute flow 36 with the extracted portion of theexhaust flow 34 discussed above, thereby diluting the extracted portion.An outlet of the dilution device may be fluidly connected to an inlet ofthe filter 62 via a flow line 26, and a valve 60 may be disposed in theflow line 26 between the dilution device 54 and the filter 62. The valve60 may be, for example, an on/off valve, and the valve 60 may bemechanically similar to, for example, the isolation valve 44 discussedabove. The valve 60 may be configured to substantially completely openor substantially completely close fluid communication between thedilution device 54 and the filter 62.

The filter 62 may be, for example, a particulate matter filter and/orany other type of exhaust flow filter known in the art. Such types offilters may include, for example, a foam cordierite centered metal, orsilicon carbide type filter. The filter 62 may include, for example,filter media, and the filter media may be made of any material useful inremoving pollutants from a flow of gas passing therethrough. In anexemplary embodiment of the present disclosure, the filter media maycontain catalyst materials capable of collecting, for example, soot,NOx, sulfur compounds, particulate matter, and/or other pollutants knownin the art. Such catalyst materials may include, for example, alumina,platinum, rhodium, barium, cerium, and/or alkali metals, alkaline-earthmetals, rare earth metals, or combinations thereof. The filter media maybe situated horizontally, vertically, radially, or heliacally. Thefilter media may also be situated in a honeycomb, mesh, or any otherconfiguration so as to maximize the surface area available for trapping,collecting, filtering, and/or removing pollutants.

In an exemplary embodiment of the present disclosure, one or morediagnostic devices 70 may be disposed proximate an inlet and/or anoutlet of, for example the dilution device 54, the filter 62, and/orother components of the exhaust sampling system 20. The diagnosticdevices 70 may be, for example, internal to or external from thecomponents of the exhaust sampling system 20, and may be, for example,fluidly connected to one or more of the flow lines 26 of the exhaustsampling system 20. The diagnostic devices 70 may be any sensing devicesknown in the art such as, for example, flow meters, emission meters,particle size sensors, pressure transducers, radio devices, or othersensing and/or sampling devices configured to sense engine emissions.Such diagnostic devices 70 may sense, for example, soot and/or NOxlevel, temperature, pressure, and/or other flow characteristics. Each ofthe diagnostic devices 70 may be electrically connected to the exhaustsampling system controller 22 and may be configured to send sensedinformation to the exhaust sampling system controller 22 via controllines 32. As shown in FIG. 2, in an exemplary embodiment, the diagnosticdevice 70 associated with the filter 62 may be, for example, adifferential pressure transducer configured to sense the pressure dropacross the filter 62. Such an exemplary diagnostic device may be fluidlyconnected proximate an inlet of the filter 62 and proximate an outlet ofthe filter 62.

In an exemplary embodiment of the present disclosure, the exhaustsampling system 20 may further include a thermistor 59. The thermistor59 may be, for example, a resistor, a temperature sensitivesemi-conductor, and/or any other type of temperature sensor known in theart. The thermistor 59 may be, for example, a fast response thermistor,and may include materials or components whose resistance changes rapidlywhen exposed to a change in temperature. As illustrated in FIG. 2, acomponent of the thermistor 59 may be fluidly connected to the exhaustline 58 and the thermistor 59 may be configured to sense changes intemperature of the exhaust flow 34 passing therethrough. The thermistor59 may be electrically connected to, for example, the exhaust samplingsystem controller 22 and may be configured to transmit, for example,sensed temperature, flow, and/or other information thereto. It isunderstood that, in other exemplary embodiments of the presentdisclosure, the thermistor 59 may be omitted.

The dilute side 106 of the exhaust sampling system 20 may be connectedto the total side 108 via a bypass line 66 fluidly connecting the valve52 to a valve 64. An outlet of the filter 62 may also be connected tothe valve 64 via a control line 26. Accordingly, during use a diluteflow 36 may be directed through the valve 52 to valve 64, via the bypassline 66, thereby bypassing, for example, the dilution device 54 and thefilter 62. Alternatively, the dilute flow 36 may be directed throughvalve 52 to the dilution device 54 and the filter 62 before passingthrough the valve 64, and the valve 52 may prohibit flow from passingfrom the dilute side through the bypass line 66. As discussed above withrespect to valve 52, the valve 64 may be, for example, a two-way valve,a three-way valve, or any other type of controllable flow valve known inthe art. The valve 64 may be sized and/or otherwise configured to allowany range of flow to pass from the filter 62 to downstream components onthe total side 108 of the exhaust sampling system 20. Accordingly, thevalve 64 may be sized to handle larger flow volumes (i.e. combinedflows) than the valve 52. An outlet of the valve 64 may be fluidlyconnected to an inlet of a flow control valve 74 via a flow line 26.

The flow control valve 74 may be structurally similar to the flowcontrol valve 50 discussed above with respect to the dilute side 106 ofthe exhaust sampling system 20. As illustrated in FIG. 2 a flow line 27may be fluidly connected between valve 64 and flow control valve 74. Avalve 68 may be fluidly connected to the flow line 27 and configured toreceive at least a portion of the flow exiting an outlet of the valve64. The valve 68 may be any two-way or three-way valve known in the art.The valve 68 may be configured to allow a flow of ambient air 72 to passthrough the flow line 27 to the flow control valve 74. Alternatively thevalve 68 may be configured to receive a portion of the flow exitingvalve 64 for sensing. A diagnostic device 70 may be fluidly connected toan outlet of the valve 68 to assist in sensing the flow received fromvalve 64.

In an exemplary embodiment, the diagnostic device 70 fluidly connectedto the outlet of the valve 68 may be, for example, a flow meter sized tomeasure a flow through the valve 68. The flow through the valve 68 maybe, for example, volumetrically analogous to the flow through theextraction component 56. In such an exemplary embodiment, valve 52 andvalve 64 may be controlled to direct a dilute flow 36 to valve 68,therefore bypassing the dilution device 54 and the filter 62. Forexample, during an quality control check, the flow sensor 76, the flowcontrol valve 74, the flow sensor 46, the venturi 48, and the flowcontrol valve 50 may be placed in series, and a flow potential may becreated by the vacuum 80 and the compressed air source 38. In addition,during the exemplary quality control check, the flow through the flowsensor 46 may be set to, for example, 85 liters per minute and the flowthrough a flow sensor 76 may be set to, for example, 100 liters perminute. The difference between these two flows may be a flow of ambientair drawn through the valve 68 (represented by flow arrow 72). Thevolume of the flow of ambient air may be substantially the same as theflow of exhaust gas that would be extracted by the extraction component56 if the exhaust sampling system 20 was sampling exhaust gas. It isunderstood, however, that at any given time during operation, the flowthrough the extraction component 56 cannot be simultaneously identicalto the flow through diagnostic device 70 proximate the valve 68.

It is understood that directly measuring the volume and/or othercharacteristics of the flow extracted from the power source exhaust flowby the extraction component 56 may be difficult. For example, directlymeasuring the amount of flow extracted from the exhaust flow may quicklycontaminate any flow meter, or other device used to measure the flowdirectly, with particulate matter. In addition, the extracted flow mayhave a temperature in excess of 600° C. and thus conventional flowmeters may not be suitable for measuring such high temperature flows.Accordingly, due to the difficulties associated with measuring theextracted flow with an inline flow meter, measuring the extracted flowwith a diagnostic device 70 as described above may be helpful.

An outlet of the flow control valve 74 may be fluidly connected to aflow sensor 76 via a flow line 26. The flow sensor 76 may be configuredto measure, for example, the pressure, volume, mass, and/or othercharacteristics of the flow passing through the total side 108 of theexhaust sampling system 20. The flow sensor 76 may be any type of flowsensor known in the art In an exemplary embodiment, the flow sensor 76may be a volumetric device similar to the flow sensor 46 discussed abovewith respect to the dilute side 106. Thus, the flow sensor 76 mayinclude a laminar flow element and a number of additional componentsconfigured to assist in calculating the mass flow passing through theflow sensor 76. Such components may include, for example, a platinumresistance thermistor and an absolute pressure transducer. It isunderstood that while a pressure transducer configured to measurepressure drop may be associated with the laminar flow element of theflow sensor 46, in an exemplary embodiment of the present disclosure, acorresponding pressure transducer may not be required to sense and/ormeasure the pressure drop across, for example, the flow sensor 76. Inaddition, as discussed above with respect to the flow sensor 46 thecomponents of the flow sensor 76 may be configured to assist in definingthe density of the flow passing through the flow sensor 76. Accordingly,the flow sensor 76 may configured to measure the mass of the flowpassing therethrough.

In an exemplary embodiment, the flow sensor 76 may include a positivedisplacement type flow meter. Such a flow meter may include, forexample, one or more sets of lobes disposed on meshed gears (not shown).Such gears may be constructed of, for example, aluminum, stainlesssteel, platinum, and/or any other like metals, and may be very finelymachined so as to reduce friction and/or resistance between each otherwhen meshing. In an exemplary embodiment, as flow is directed throughthe flow sensor 76, the internal lobes and/or gears may be moved and/orturned by the flow in direct proportion to the amount of flow beingdirected through the flow sensor 76.

An outlet of the flow sensor 76 may be fluidly connected to a valve 78via a flow line 26. The valve 78 may be structurally similar to theisolation valve 44 discussed above with respect to the dilute side 106.Accordingly the valve 78 may be configured to substantially open and/orsubstantially close fluid communication between the flow sensor 76 andthe vacuum 80 of the exhaust sampling system 20. The vacuum 80 may beany conventional source of negative pressure known in the art. Thevacuum 80 may include, for example a shop vacuum, a vacuum pump, and/orany other device capable of creating negative pressure. The vacuum 80may be of any power or capacity useful in drawing flow through anexhaust sampling system such as the exhaust sampling 20 illustrated inFIG. 2. In an exemplary embodiment of the present disclosure, the vacuum80 may be configured to have a low pressure spike signature. Such avacuum 80 may be configured to direct a substantially constant negativepressure to components of the exhaust sampling system 20.

INDUSTRIAL APPLICABILITY

The disclosed exhaust sampling system 20 may be used with any diesel,gasoline, natural gas, and/or other combustion engines, furnaces, orpower sources known in the art. As discussed above, the exhaust samplingsystem 20 may be used for testing, design, development, and/orcertification of such power sources. It is understood that such powersources may be used in conjunction with any machine, on-road vehicle,off-road vehicle, stationary machine, and/or other exhaust producingdevices known in the art.

A method for using the disclosed exhaust sampling system 20 to certifyan exemplary power source will now be discussed with respect to thesampling strategy 84 illustrated in FIG. 3. It is understood thatgovernment regulations may require different testing scenarios dependingupon the particular power source being certified. For example, somepower sources may be certified under a steady state flow condition,while other power sources may be certified under transient flowconditions. As used herein, the term “transient flow condition” meansflow conditions which are altered, modified, and/or otherwise changedduring a test cycle. The exhaust sampling system 20 of the presentdisclosure may be used to certify power systems in both the transientand the steady state flow conditions. For the purposes of the presentdiscussion, however, only a transient flow condition certificationmethod will be discussed.

To begin using the exhaust sampling system 20 illustrated in FIG. 2, theuser may bring the system 20 to thermal equilibrium. In thermalequilibrium, each component of the exhaust sampling system 20 may be atsubstantially the same temperature and, in an exemplary embodiment, thenominal temperature may be approximately 30 degrees Celsius. It isunderstood that, for example, the filter 62 and its components must bemaintained at a temperature of approximately 47 degrees Celsius (plus orminus, approximately, five degrees Celsius) for certification purposes.Once thermal equilibrium has been reached, the user may keep the systemrunning at idle until sampling begins. In order to achieve thermalequilibrium, the user may, for example, set a desired combined flow rateand a desired dilute flow rate. The desired dilute flow rate maycorrespond to the volume of dilute flow 36 that is to be directed to thedilution device 54 via the flow control valve 50. The desired combinedflow rate may correspond to the volume of the combined flow 37 that isto be directed to the filter 62 on the total side 108 of the exhaustsampling system 20.

While the system is being brought to thermal equilibrium, the diluteflow 36 may pass through the compressed air source 38, the flowtreatment assembly 40, the chiller 42, the open isolation valve 44, theflow sensor 46, and the open flow control valve 50. The valve 52 maythen direct the dilute flow 36 through the dilution device 54 and maysubstantially fluidly seal the bypass line 66. In addition, the valve 60may be substantially closed, thus, the dilute flow 36 may be directedthrough the extraction component 56 to dislodge, for example, spuriousparticulate and/or other foreign matter that may have built up thereinwhile the exhaust sampling system 20 was idle. The dilute flow 36 maythen join the exhaust flow 34 and may be removed by the evacuationsystem 18 of the test cell 100. As illustrated in FIG. 2, a flow of gas82 may be created by opening the valve 68 to allow a flow of ambient airto enter the valve 68, as illustrated by flow arrow 72. Alternatively,the operator can control the valves to extract a sample of the exhaustflow 34 and direct the sample through the filter 62. The operator maydiscard the filter media after extracting a sample during warm-up.

Once the exhaust sampling system 20 has reached thermal equilibrium, theuser may calibrate the system (step 86). During calibration, the usermay calibrate the dilute side 106 of the exhaust sampling system to thetotal side 108 in order to derive, for example, one or more polynomialsfor use in a control algorithm during sampling. In particular, duringcalibration the valve 44 and the flow control valve 50 may remain openand the valve 52 may direct the dilute flow 36 through the bypass line66 to the valve 64. The dilute flow 36 may them pass to the flow controlvalve 74 and the valve 68 may be fully closed such that none of thedilute flow 36 may pass through flow line 27. In such a configuration,the flow sensor 46 may be put in series with the flow sensor 76. Theexhaust sampling system 20 may be operated throughout a series of flowpoints specified by the user. By using the flow sensor 46, the flowsensor 76, and/or other components of the exhaust sampling system 20 tomeasure the dilute flow 36 at each of the flow points, the exhaustsampling system controller 22 may calculate a polynomial that representsthe relationship between the flow sensor 46 and the flow sensor 76. Thispolynomial may be used to mathematically correct the flow measurementsmade by the flow sensor 46 to the flow measurements may by sensor 76during operation of the exhaust sampling system 20.

After calibration, the operator may install a test filter mediacartridge into the filter 62 and may control the engine to a first testpoint using the test cell controller 24. At the first test point, one ormore diagnostic devices 70 of the exhaust sampling system 20 and/or thetest cell 100 may sense one or more operating characteristics of thepower source 10 (step 88). Such operating characteristics may include,for example, the flow of air to an intake of the power source 10, therate of fuel consumption, power source temperature, and/or the mass flowrate of the exhaust flow 34. Based on the sensed operatingcharacteristics described above, the exhaust sampling system controller22 may calculate a desired mass flow of the extracted flow (step 90).The calculated desired mass flow of the extracted flow may correspond tothe desired amount of exhaust flow to be extracted from the exhaust flow34. In addition, the desired extracted mass flow may be substantiallyproportional to the mass flow of the exhaust flow 34.

The exhaust sampling system controller 22 may then control thecomponents of the exhaust sampling system 20 to extract the calculateddesired portion of the exhaust flow 34 (step 92). The exhaust samplingsystem controller 22 may also control the compressor 38 flow treatmentassembly 40, chiller 42, flow sensor 46 and/or flow control valve 50 todirect a dilute flow 36 to the dilution device 54 in order to dilute theextracted portion of the power source exhaust flow (step 94). It isunderstood that, as used herein, the term “dilution” means mixing a flowof extracted exhaust with a flow of ambient air so as to simulateenvironmental conditions such as pressure and/or temperature. It isunderstood that during operation of the exhaust sampling system 20 thecomponents of the exhaust sampling system 20 may operate at relativelyhigh dilution ratios (i.e., the flow rate of the dilute flow 36 relativeto the flow rate of the extracted flow may be relatively high). Suchhigh dilution ratios may be required in order to reduce the temperatureof the extracted flow to approximately 52° C. before the combined flow37 reaches the filter 62.

During use, the exhaust sampling system 20 may substantiallycontinuously and substantially instantly control the difference betweenthe combined flow 37 and the dilute flow 36 with the flow control valves74, 50 respectively. By controlling the difference between the flows 37,36 in this way, the user may control, for example, the volume of theflow that is extracted from the exhaust flow 34 because the volume ofthe combined flow 37 is equal to the volume of the dilute flow 36 plusthe volume of the extracted flow. Accordingly, by controlling thedifference between the combined flow 37 and the dilute flow 36, the usermay accurately control the proportionality of the extracted flow duringa transient test cycle. Such a control strategy may be advantageoussince it takes into account excursions in the exhaust flow 34 withoutdirectly sensing, for example, the mass flow rate and/or othercharacteristics of the exhaust flow 34 or the extracted flow. Inaddition, such a control strategy avoids the difficulties of directlymeasuring such flows discussed above.

The exhaust sampling system 20 may be controlled to ensure that theinstantaneous difference between the total side mass flow and the diluteside mass flow is continually proportional to the power source exhaustmass flow. In order to achieve this, the exhaust gas sampling systemcontroller 22 may be configured to continually monitor the operatingcharacteristics of the power source 10 described above with respect tostep 88, and calculate system flow set points which yield proportionalsampling. In particular, in transient certification trials in which thepower source 10 is challenged to instantaneous changes in exhaust flowrate, the components of the exhaust sampling system 20 may be configuredto react to those changes within less than or equal to 500 milliseconds.

The combined flow 37 may pass from the dilution device 54 to the filter62, whereby the particulates contained within the combined flow 37 maybe extracted and trapped within the filter media. The filtered combinedflow 37 may then pass from the filter 62, through valve 64, and throughthe flow control valve 74 to the flow sensor 76 where a gravimetric massdetermination may be made (step 96). Sensed information may betransmitted from one or more components of the flow sensor 76 to theexhaust sampling system controller 22, and the exhaust sampling systemcontroller 22 may store and/or present the sensed data to the operatoror user (step 98).

The combined flow 37 may then pass from the flow sensor 76, through theopen valve 78, and to the vacuum 80. The combined flow 37 may exit theexhaust sampling system 20 as illustrated by flow arrow 82. Once anadequate amount of data has been collected and/or stored by the exhaustsampling system controller 22, the exhaust sampling system controller 22may determine whether or not continued sampling may be required for thepurposes of certification (step 102). If continued sampling is required,the exhaust sampling system controller 22 may continue to senseoperating characteristics of the power source 10 as described above(step 88). Alternatively, if a sufficient amount of data has beenacquired the exhaust sampling system controller 22 may stop sampling(step 104). It is understood that in a transient certificationprocedure, the user may operate the power source 10 through a variety ofdifferent throttle and/or other set points. During such a procedure, theexhaust sampling system 20 may continuously sense the operatingcharacteristics of the power source 10 and may continuously vary theflow rate of the dilute flow 36 delivered to the dilution device 54 inresponse to the sensed operating characteristics of the power source 10,as well as the sensed flow rate of the combined flow 37 passing throughthe total side 108 of the exhaust sampling system 20.

It is understood that, in an exemplary embodiment, the exhaust samplingsystem 20 may also be controlled to slow its transient response inapplications where a relatively low output power source 10 is connectedto a relatively large volume exhaust system, such as, for example, oneor more relatively large volume components of the test cell 100. Duringuse, the thermistor 59 may sense changes in the temperature of theexhaust flow 34 and may send the sensed temperature information to theexhaust sampling system controller 22. The exhaust sampling systemcontroller 22 may calculate the volumetric flow rate of the exhaust flow34 based on, for example, the temperature input received from thethermistor 59 and the mass flow rate of the exhaust flow 34 discussedabove. In an exemplary embodiment, the exhaust sampling systemcontroller 22 may calculate the volumetric flow rate at approximately 80Hz, and the test cell operator may input the volume of the exhaustsystem based on the length and diameter of, for example, the exhaustline 58. If the time it takes for a particle to travel in the exhaustflow 34 between, for example, the power source 10 and the extractioncomponent 56 exceeds the known response time of the exhaust samplingsystem 20, the exhaust sampling system controller 22 may delay theproportional response of the exhaust sampling system 20 through controlof, for example, the flow control valve 50. For example, if the knownresponse time of the exhaust sampling system 20 is 200 milliseconds andthe calculated travel time of a particle between the power source 10 andthe extraction component 56 is 300 milliseconds at a given instant, theexhaust sampling system controller 22 may delay a transient response bythe exhaust sampling system 20 by 100 milliseconds.

Other embodiments of the disclosed exhaust sampling system 20 will beapparent to those skilled in the art from consideration of thespecification. For example, the isolation valve 44 and the valve 78 maybe three way valves configured to direct a flow of fluid from a flowline 26 to other locations within the exhaust sampling system 20. Inaddition, the filter 62 may be fitted with one or more bosses to assistin inserting and/or removing the test filter media cartridge. It isintended that the specification and examples be considered as exemplaryonly, with the true scope of the invention being indicated by thefollowing claims.

1. A method for controlling the flow through an exhaust sampling system,comprising: sensing an operating characteristic of a power source;extracting a sample of an exhaust flow of the power source; combiningthe sample with an additional flow of fluid; and measuring a particulatelevel of the combined flow, wherein a flow rate of the extracted sampleis controlled to be substantially proportional to a flow rate of theexhaust flow based on a difference between the combined flow and theadditional flow.
 2. The method of claim 1, further including calibratinga dilute side of the exhaust sampling system to a total side of theexhaust sampling system.
 3. The method of claim 1, wherein the operatingcharacteristic includes at least one of an intake air mass flow of thepower source, an exhaust mass flow of the power source, and a fuel massflow.
 4. The method of claim 1, wherein the additional flow includes aflow of treated ambient air.
 5. The method of claim 1, wherein a flowrate of the combined flow is equal to the sum of a flow rate of thesample and a flow rate of the additional flow.
 6. The method of claim 1,further including sensing a flow rate of the combined flow.
 7. Themethod of claim 6, further including calculating an amount of exhaust tobe extracted based on the sensed flow rate of the combined flow and theoperating characteristic.
 8. A method of controlling fluid flow throughan exhaust sampling system connected to a power source, comprising:controllably extracting a portion of an exhaust flow of the powersource; directing the portion through a dilution device; and combiningthe portion with a treated flow of fluid, wherein a mass flow rate ofthe extracted portion is controlled to be substantially proportional toa mass flow rate of the exhaust flow of the power source based on adifference between a mass flow rate of the combined flow and a mass flowrate of the treated flow.
 9. The method of claim 8, further includingsensing an operating characteristic of the power source.
 10. The methodof claim 9, wherein the operating characteristic includes at least oneof an intake air mass flow of the power source, an exhaust mass flow ofthe power source, and a fuel mass flow.
 11. The method of claim 9,wherein the flow rate of the extracted portion is controlled based on atleast one of the sensed operating characteristics.
 12. The method ofclaim 11, wherein the at least one of the sensed operatingcharacteristics includes the mass flow rate of the exhaust flow of thepower source.
 13. The method of claim 9, further including controllingthe mass flow rate of the extracted portion in response to the sensedoperating characteristic.
 14. The method of claim 13, wherein the systemis configured to modify the mass flow rate of the extracted portion inresponse to the sensed operating characteristic in 500 milliseconds orless.
 15. The method of claim 9, wherein the mass flow rate of theextracted portion is substantially continuously controlled to besubstantially proportional to the mass flow rate of the exhaust flowduring a transient test cycle.
 16. An exhaust sampling system,comprising: a first flow sensor fluidly connected to a compressed airsource and configured to sense a characteristic of a dilute flow; a flowcontrol valve fluidly connected to the first flow sensor and configuredto controllably direct the dilute flow to a dilution device; a secondflow sensor fluidly connected downstream of the dilution device andconfigured to sense a characteristic of a combined flow; and acontroller configured to control a mass flow rate of a flow of exhaustgas extracted by a component of the dilution device based on adifference between the sensed characteristic of the dilute flow and thesensed characteristic of the combined flow.
 17. The exhaust samplingsystem of claim 16, wherein the flow control valve is configured tosubstantially continuously control the dilute flow in response to thesensed characteristic of the dilute flow and the sensed characteristicof the combined flow.
 18. The exhaust sampling system of claim 16,wherein the flow control valve is configured to respond to changes inthe sensed characteristic of the dilute flow and the sensedcharacteristic of the combined flow in 500 milliseconds or less.
 19. Theexhaust sampling system of claim 16, further including a second flowcontrol valve fluidly connected to the second flow sensor and configuredto controllably direct the combined flow to the second flow sensor. 20.The exhaust sampling system of claim 16, wherein at least one of thefirst and second flow sensors comprises a laminar flow element.